perhaps a dumb query, but ...

As to CARA--well I would like to say our company developed it, but that's not the case. It's developed out of Germany. We sell the CARA software and we use it sparingly as a validation tool on some of our room designs. CARA does not do everything--but it does enough very well that we value it tremendously. CARA is a fabulous software, and you can "build" almost any loudspeaker in the speaker editor. We firmly believe in the CARA product and work with their developers to improve the program. I agree they should have more speakers, but at the price they sell the software, they look for the speaker companies to put together the information rather than for them to go and proactively obtain all speaker data. Quite honestly, if they can remain profitable and provide the level of software they have at $50 a copy--more power to them. If they had to get all speaker data it would probably mean the software would be $250.

what I mean by "dipolar bass" is any loudspeaker with dipolar woofer characteristics, posted on July 13, 2003 at 20:49:18

Mart
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Posts: 31273
Location: upstate NY
Joined: June 6, 2001
Contributor
Since: June 25, 2000

... maybe a Martin Logan CLS IIz and/or Statement and/or Acoustat and/or VMPS and/or Apogee. I didn't expect my particular speakers listed for the price point nor would I expect my one rough-hewn brick wall to be modeled, but I was hoping for something informative/instructional. Dipolar bass management is so much trickier than monopolar that purchasing software would be advisable. Consequently, because it is more complex, it isn't addressed. Is this a classic catch-22 or what? I was hoping that I over-looked a speaker like a AR:Tympani or an old Infinity:planar something but I guess not.
... just my 2¢♪ moderate Mart £ ♫☺ Planar Asylum

Re: what I mean by "dipolar bass" is any loudspeaker with dipolar woofer characteristics, posted on July 13, 2003 at 21:27:04

Rives
Manufacturer

Posts: 179
Location: Maryland
Joined: January 4, 2003

Actually it's not as tricky as you might have thought. It's really the upper frequencies that the dipole is tricky. Low frequencies do not have the same issues. Whether they are dipole or bipole the distance and phase shift between the drivers is so small relative to the wavelengths they are producing it's theoretically not a concern. Mind you, in practical terms, there is a difference because even at low frequencies the pressure created from a speaker in the rear against a rear wall is different from that of the front. You can also purposely change phase shifts of two speakers to have cancellations at certain frequencies (this definitely goes beyond the scope of CARA).

Also, you should note that there are user files of speakers on the CARA website. Every now and then you can find one that CARA does not include. You can also update your files to CARA.

actually, I find the dipolar upper frequencies vastly simplier, posted on July 13, 2003 at 22:19:41

Mart
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Posts: 31273
Location: upstate NY
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... the comb filter is easily fixed with judicious dispersion & open-cell foam. Even toing in of the speaker helps via non-uniform reflected distances. All problems abov 1kHz is nearly irrelevent.

However, in the long-wavelength bass region, these tricks don't help much. What you do have is a classic figure-8 dispersion pattern that is a function of the speaker's bas cnceling backwall reflections, listener's backwall reflections, & a transistion from line to point-source dispersion drop-off. These issues as well as room resonance can get complicated, especially if one is exciting a mode1W transverse wave. Just how much less important is this mode with strictly indirect wave energy? We all recognize it is significant, but how much? 10dB? 20dB?

... just my 2¢

♪ moderate Mart £ ♫☺ Planar Asylum

oh, I bet I know what you're referring to ..., posted on July 13, 2003 at 22:24:07
Mart Bored Member Posts: 31273 Location: upstate NY Joined: June 6, 2001 Contributor Since: June 25, 2000	... the 1st reflection point. That's crucial for all line-sources, regardless of monopolar, dipolar, or bipolar. ... just my 2¢♪ moderate Mart £ ♫☺ Planar Asylum

Re: actually, I find the dipolar upper frequencies vastly simplier, posted on July 14, 2003 at 05:51:10

Rives
Manufacturer

Posts: 179
Location: Maryland
Joined: January 4, 2003

It depends on the energy dispersion of a speaker. The bass approaches a point source and having dipoles just fills in that gap behind the speaker. If you look at an off axis for a full 360 degrees of the speaker then you can determine how important it is. Theory states that the cabinet size is small less than 1/8 of the wavelengths we are producing then off axis response should remain constant all around the speaker (I'm speaking of bass frequencies only here). This is usually true to a degree, but there is less energy in the back of the speaker at the upper bass frequencies.

Getting to indirect energy for modes--modes are comprised of nearly all indirect energy. This is probably not what you were considering, but for true direct energy in a mode, the speaker has to be placed at the peak of the mode and beat at that frequency. Otherwise, it's indirect and is a result of the walls pressurizing and causing a beat at that frequency. I hope that's clear--don't know if I stated it very well. I do understand that wasn't really what you were getting at--if power is disappated greater in the front of the speaker than the sides, then are the W modes excited significantly less and how much less. I don't know the answer to this. It would be interesting to have a speaker that had a very large cabinet, thus was not omni directional at the bass frequencies (or a particular frequency of the modes of a room) and measure the difference in the modes depending on orientation and placement relative to that mode. Placement dependencies are well known, and I imagine that their significance is so dominant over power disappation issues that the power disappation issues are near negligible.

While we spend a lot of time measuring speakers in listening rooms and doing theoretical calculations, we are not speaker designers. It would be good if a speaker engineer commented on this as well.

As to the back wave for mid and upper frequencies for planers. You do need judicious dispersion and absorption, sometimes resonation as well. The hard part is that "judicious" thing. You want to cross over the dispersion (and the dispersion bandwidth is critical) at around 1.25k to absorption, but the absorption curve is pretty critical so that you have an even frequency response in terms of energy time functions. If you have an easy way of calculating this in room we would love to know about it--because it takes us a long time and is very dependent on the rest of the room to get it right.

"Dipolar bass management is so much trickier "???, posted on July 14, 2003 at 08:28:08

Richard BassNut Greene

I'd say dipole bass management was easier.

Since dipole bass drivers excite the side-to-side-wall and
floor-to-ceiling room modes less than monopole bass drivers,
they usually produce clearer bass frequencies when there are
no bass traps or parametric EQ used. Dipole basss drivers do
excite the front-to-back wall room modes just like monopole bass drivers so problems with that room mode (very common in my experience) won't go away.

Below the lowest frequency room mode, dipole bass driver will not get the free 12dB/octave cabin gain that monopole bass drivers generate.

Re: actually, I find the dipolar upper frequencies vastly simplier, posted on July 15, 2003 at 14:47:52
Mart Bored Member Posts: 31273 Location: upstate NY Joined: June 6, 2001 Contributor Since: June 25, 2000	We at the Planar Asylum love acoustic lenses & Ficus trees. I, OTOH, just monopolarized my Magnepan's HFs by eggcrating the entire backwave as depicted here. ... just my 2¢♪ moderate Mart £ ♫☺ Planar Asylum

Re: "Dipolar bass management is so much trickier "???, posted on July 15, 2003 at 14:52:56
Mart Bored Member Posts: 31273 Location: upstate NY Joined: June 6, 2001 Contributor Since: June 25, 2000	That's part of the problem. Most speakers blend resonance frequencies which makes them tend to average out whereas planars have enormous SPL swings. ... just my 2¢♪ moderate Mart £ ♫☺ Planar Asylum

Room Acoustics Forum by Rives Audio

perhaps a dumb query, but ...

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